TypeKindVisitor8.java revision 2571:10fc81ac75b4 
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14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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25
26package javax.lang.model.util;
27
28import javax.annotation.processing.SupportedSourceVersion;
29import javax.lang.model.SourceVersion;
30import javax.lang.model.type.*;
31import static javax.lang.model.SourceVersion.*;
32
33/**
34 * A visitor of types based on their {@linkplain TypeKind kind} with
35 * default behavior appropriate for the {@link SourceVersion#RELEASE_8
36 * RELEASE_8} source version.  For {@linkplain
37 * TypeMirror types} <tt><i>XYZ</i></tt> that may have more than one
38 * kind, the <tt>visit<i>XYZ</i></tt> methods in this class delegate
39 * to the <tt>visit<i>XYZKind</i></tt> method corresponding to the
40 * first argument's kind.  The <tt>visit<i>XYZKind</i></tt> methods
41 * call {@link #defaultAction defaultAction}, passing their arguments
42 * to {@code defaultAction}'s corresponding parameters.
43 *
44 * <p> Methods in this class may be overridden subject to their
45 * general contract.  Note that annotating methods in concrete
46 * subclasses with {@link java.lang.Override @Override} will help
47 * ensure that methods are overridden as intended.
48 *
49 * <p> <b>WARNING:</b> The {@code TypeVisitor} interface implemented
50 * by this class may have methods added to it in the future to
51 * accommodate new, currently unknown, language structures added to
52 * future versions of the Java&trade; programming language.
53 * Therefore, methods whose names begin with {@code "visit"} may be
54 * added to this class in the future; to avoid incompatibilities,
55 * classes which extend this class should not declare any instance
56 * methods with names beginning with {@code "visit"}.
57 *
58 * <p>When such a new visit method is added, the default
59 * implementation in this class will be to call the {@link
60 * #visitUnknown visitUnknown} method.  A new type kind visitor class
61 * will also be introduced to correspond to the new language level;
62 * this visitor will have different default behavior for the visit
63 * method in question.  When the new visitor is introduced, all or
64 * portions of this visitor may be deprecated.
65 *
66 * <p>Note that adding a default implementation of a new visit method
67 * in a visitor class will occur instead of adding a <em>default
68 * method</em> directly in the visitor interface since a Java SE 8
69 * language feature cannot be used to this version of the API since
70 * this version is required to be runnable on Java SE 7
71 * implementations.  Future versions of the API that are only required
72 * to run on Java SE 8 and later may take advantage of default methods
73 * in this situation.
74 *
75 * @param <R> the return type of this visitor's methods.  Use {@link
76 *            Void} for visitors that do not need to return results.
77 * @param <P> the type of the additional parameter to this visitor's
78 *            methods.  Use {@code Void} for visitors that do not need an
79 *            additional parameter.
80 *
81 * @see TypeKindVisitor6
82 * @see TypeKindVisitor7
83 * @since 1.8
84 */
85@SupportedSourceVersion(RELEASE_8)
86public class TypeKindVisitor8<R, P> extends TypeKindVisitor7<R, P> {
87    /**
88     * Constructor for concrete subclasses to call; uses {@code null}
89     * for the default value.
90     */
91    protected TypeKindVisitor8() {
92        super(null);
93    }
94
95    /**
96     * Constructor for concrete subclasses to call; uses the argument
97     * for the default value.
98     *
99     * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
100     */
101    protected TypeKindVisitor8(R defaultValue) {
102        super(defaultValue);
103    }
104
105    /**
106     * This implementation visits an {@code IntersectionType} by calling
107     * {@code defaultAction}.
108     *
109     * @param t  {@inheritDoc}
110     * @param p  {@inheritDoc}
111     * @return the result of {@code defaultAction}
112     */
113    @Override
114    public R visitIntersection(IntersectionType t, P p) {
115        return defaultAction(t, p);
116    }
117}
118